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- Towards the recovery of by-product metals from mine wastes : an X-Ray absorption spectroscopy study on the binding state of rhenium in debris from a centennial Iberian Pyrite Belt minePublication . Figueiredo, M. Ondina; Silva, Teresa; Veiga, JP; de Oliveira, Daniel Pipa Soares; Batista, Maria JoaoRhenium is a very scarce element, occurring in the Earth's crust mainly carried by molybdenite (MoS2). Due to a very low availability comparative to actual industrial demand, rhenium is nowadays one of the most expensive mineral commodities and an increased interest is focused on exploring residues resulting from a long-term mining, particularly of sulphide ore deposits. It is therefore noteworthy to assign the presence of rhenium (in a concentration up to 3 ppm) in the waste materials from the old sulphur factory at the abandoned mine of São Domingos (Iberian Pyrite Belt, Southeast Portugal), exploited since the Roman occupation of Iberia. Aiming at a potential sustainable recovery of rhenium as a by-product, X-ray near-edge absorption spectroscopy (XANES) was applied to clarify the Re-binding and mode of occurrence by comparing Re L3-edge XANES spectra obtained from mine waste samples (previously fully characterized by X-ray laboratory techniques) with similar spectra collected from Re-rich molybdenites (Mo1-xRexS2) and from Re-O model compounds configuring various valences and coordination environments of rhenium ions. Obtained results are commented, ruling out a possible Re-S binding and rather conforming with the binding of rhenium to oxygen in the analysed mine waste materials.
- Selenium in wastes from the old mine of São Domingos in southern Portugal (IPB) : already attached to oxygen or retained in relics of former chalcogenide minerals?Publication . Figueiredo, M. Ondina; Silva, Teresa; Veiga, JP; Batista, Maria Joao; Salas-Colera, Eduardo; de Oliveira, Daniel Pipa Soares
- Rhenium in waste material of the sulphur factory from the S. Domingos abandoned mine (Iberian Pyrite Belt, southern Portugal) : an X-ray absorption spectroscopy approachPublication . Figueiredo, M. Ondina; Silva, Teresa; Veiga, JP; de Oliveira, Daniel Pipa Soares; Batista, Maria Joao
- Fingerprints for mining products and wastes of the S. Domingos, Aljustrel and Neves Corvo mines : a sustainable perspectivePublication . Batista, Maria Joao; Matos, João Xavier; Figueiredo, M. Ondina; de Oliveira, Daniel Pipa Soares; Silva, Teresa; Santana, Helena; Quental, Lídia
- Mining heritage and economic potential of the wastes of the S. Domingos minePublication . Batista, Maria Joao; Matos, João Xavier; Figueiredo, M. Ondina; de Oliveira, Daniel Pipa Soares; Pereira, Zélia; Silva, Teresa; Santana, Helena; Quental, Lídia
- Selenium speciation in waste materials from an exhausted Iberian Pyrite Belt minePublication . Figueiredo, M. Ondina; Silva, Teresa; Veiga, JP; Batista, Maria Joao; Salas-Colera, Eduardo; de Oliveira, Daniel Pipa SoaresSelenium is an essential nutrient for humans, animals and microorganisms, but it becomes toxic at concentrations slightly above the nutritional levels. This naturally occurring trace element can be released to the environment from various anthropogenic sources such as mining, agricultural, petrochemical and industrial processes and its toxicity is developed along a complex cycle involving adsorption by soil components and subsequent accumulation by plants. In the environment, selenium can occur in several oxidation states ranging from selenide (Se=) to elemental selenium (Se0), selenite (Se4+) and selenate (Se6+). Selenium contents above 900 ppm were recently assigned in mine wastes from the sulphur factory at the São Domingos exhausted pyrite mine exploited in the Iberian Pyrite Belt (south Portugal) since Roman times until 1966. Aiming at a sustainable remediation of this mining site, an X-ray absorption spectroscopy study using synchrotron radiation, combined with X-ray diffraction, was undertaken to clarify the speciation state of selenium and the nature of Se-carrier phase(s). The results show that selenium does not significantly replace sulphur under the form of selenate in the dominant sulphate phases and occasionally remains as a substituting selenide anion in debris of the original sulphides present in the mine waste materials.
- X-ray absorption spectroscopy at Re L3-edge applied to mine waste materials : a possible input to the sustainable recovery of rheniumPublication . Figueiredo, M. Ondina; Silva, Teresa; Veiga, JP; de Oliveira, Daniel Pipa Soares; Batista, Maria Joao